Electrical connecting device and electrical connecting method

ABSTRACT

The present invention provides an electrical connecting member and an electrical connecting method for achieving electrical connection securely through conductive particles regardless of a slight unevenness of an object matter. An electrical connecting device ( 10 ) for electrically connecting an electrical connecting portion ( 5 ) of a first object to an electrical connecting portion ( 3 ) of a second object comprises an adhesive layer ( 6 ) disposed on the first object ( 4 ) and constituted of a plurality of conductive particles ( 7 ) and a binder ( 8 ) containing the plurality of the conductive particles ( 7 ) and a paste ( 9 ) having a fluidity and disposed on the film-like adhesive layer ( 6 ).

RELATED APPLICATION DATA

The present application is a divisional of U.S. patent application Ser.No. 09/362,057 filed Jul. 28, 1999, now U.S. Pat. No. 6,365,860 andclaims priority to Japanese Application No. P11-037471 filed Feb. 16,1999 and claims priority to Japanese Application No. P10-219216 filedAug. 3, 1998, each of which is incorporated herein by reference to theextent permitted by law.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an electrical connecting device and anelectrical connecting method for electrically connecting an electricalconnecting portion of a first object to an electrical connecting portionof a second object.

2. Description of the Related Art

With recent smaller sized and decreased thickness of electronic parts,circuits for use therein have been denser and more precise, so thatconnection of such an electronic part to a fine electrode is difficultwith conventional soldering method, rubber connector or the like.Therefore, adhesive agent and film material (hereinafter referred to asconnecting member) having anisotropy excellent in fine pitching andconductivity have been often used.

This connecting member is constituted of the adhesive agent containing apredetermined amount of conductive material such as conductive particlesand so on. This connecting member is disposed between each of protrudingelectrodes of an electronic part and a conductive pattern of a printedwiring board. By applying a pressure or heating with a pressure, theelectrodes on both the parts are electrically connected to each otherand electrodes formed adjacent each other of the same are provided withan electrical insulation. As a result, the protruding electrodes of theelectronic part and the conductive pattern of the printed wiring boardare bonded to each other and fixed.

A basic concept for making the above connecting member correspond to thefine pitch is that an insulation between adjacent electrodes is securedby making a diameter of each of conductive particles smaller than theinsulating portion between the adjacent electrodes, the containingamount of the conductive particles is set to such an extent that theparticles do not contact each other and conductivity of the connectingportion is obtained by making the conductive particles exist securely onthe electrodes.

If the diameter of the conductive particle is reduced according to theabove conventional method, however, an area of the conductive particlesurface increases remarkably so that a secondary cohesion occurs,thereby combining adjacent particles with each other. As a result, theinsulation between the adjacent electrodes cannot be maintained. If thecontaining amount of the conductive particles decreases, the number ofthe conductive particles on electrodes to be connected also decreases sothat the number of contacting points becomes short. As a result, theconduction between the connecting electrodes cannot be obtained.Consequently, it is difficult to make the connecting member correspondto fine pitch while a long term connecting reliability is maintained.

That is, by a remarkable correspondence to the fine pitch trend,miniaturization of an electrode area and a gap (space) between adjacentelectrodes have progressed, so that the conductive particles on theelectrodes flows out between the adjacent electrodes with adhesive agentbecause of pressurization at the time of connection or heating with apressure.

To solve such a problem, conventionally, a connecting member in which bycoating the conductive particles for insulation, a quantity of theconductive particles in the connecting member is increased and aconnecting member constituted of an adhesive layer containing theconductive particles and a layer not containing them have been proposed.

FIGS. 1 and 2 show these conventional connecting members.

In case where an object is a glass substrate 200 as shown in FIG. 1,flatness of a mounting region for an IC ( integrated circuit) 201 inglass substrate 200 is about ±0.5 μm and if in protruding electrodes 202of the IC 201, there is few deflection (about ±0.5 μm) in the height ofeach protruding electrode like a gold plated bump, it is possible toelectrically connect the wiring pattern 203 of the glass substrate 200to the protruding electrodes 202 of the IC 201 through conductiveparticles 205 contained in a connecting member 204.

Because each of the parts such as the ICs is flat, if the thickness ofthe connecting member 204 is a height of the protruding electrode 202 ofthe IC 201 (ordinarily, about 15-25 μm and ITO pattern wired on a glassis some Angstrom) about +5 μm, the connecting member 204 is chargedsecurely under the IC 201. Therefore, the connecting member 204 does nothave to be made thicker than necessary and at the stage of temporarypressure-fitting (pressurization) of an initial period of mounting, theconductive particles 205 can be nipped between the wiring pattern 203 onthe glass substrate 200 and the protruding electrodes 202 of the IC 201.After that, even if the binder of the connecting member flows out at thetime of pressure-fitting (heating with a pressure), the nippedconductive particles 205 do not flow out, so that when the connectingmember is hardened, an electrical connection is established between thewiring pattern 203 on the glass substrate 200 and the protrudingelectrode 202 of the IC 201 through the conductive particles 205.

In FIG. 1(A), the connecting member 204 (for example, anisotropicconductive film: ACF) is bonded to the glass substrate 200. Usually, theanisotropic conductive film is bonded onto the glass substrate 200 bycarrying out ordinary heating with a pressure (heating with a pressureis performed at a pressure of about 100 N/cm² and a heating temperatureof 70-100° C.). With this state, positioning between the wiring pattern203 of the glass substrate 200 and the protruding electrode 202 of theIC 201 is carried out.

In FIG. 1(B), the IC 201 is temporarily press-fit to the glass substrate200. The temporary press-fitting of the IC 201 is carried out by only apressure or heating with a pressure (heating temperature is about70-100° C.).

In FIG. 1(C), the IC 201 is finally press-fit to the glass substrate200. The final press-fitting of the IC 201 is carried out by heatingwith a pressure. Because a temperature at this time is higher than theglass transition temperature of the anisotropic conductive film, a flowof the binder occurs. At this time, the conductive particles 205 nippedbetween the protruding electrode 202 of the IC 201 and the wiringpattern 203 of the glass substrate 200 does not flow, but the otherconductive particles 205 flow.

FIG. 1(D) shows a state in which the anisotropic conductive film ishardened. If heating with a pressure is carried out in the finalpress-fitting, after resin flows, it is hardened. This series of theabove described processes is the connecting process.

However, if the object is not a glass substrate but a printed wiringboard 300 as shown in FIG. 2, a deflection (± several μm) may begenerated in the height of the wiring pattern 303 or a deflection (±several μm) may be generated in the height of the protruding electrode202 of the IC 201 like a gold wire bump. In this case, if the thicknessof the connecting member 204 is height of the wiring pattern 303 of theprinted wiring board 300 (about 20 μm) plus height of the protrudingelectrode of the IC (about 20 μm), it is necessary to add 10-20 μm tothe above thickness by considering the safety.

In this case, because the thickness of the connecting member 204 islarge at the stage of temporary press-fitting (pressurization) of theinitial period of mounting, the conductive particles 205 cannot benipped between the wiring pattern 303 of the printed wiring board 300and the protruding electrode 202 of the IC 201. After that, when thebinder of the connecting member 204 flows at the time of finalpress-fitting (heating with a pressure), the conductive particles 205also flow. When the gap between the wiring pattern 303 of the printedwiring board 300 and the protruding electrode 202 of the IC 201coincides with the size of each of the conductive particles 205, theflowing conductive particles 205 are nipped therebetween. However, theconductive particles 205 are not concerned with every connection.Therefore, electrical connection will not be secured. Alternatively, asit is necessary to obtain parts having a strict specification, cost isincreased.

FIG. 2(A) shows a state in which the connecting member 204 (for example,anisotropic conductive film) is bonded to the printed wiring board 300.The anisotropic conductive film is pasted onto the printed wiring board300 by normal heating with a pressure (this heating with a pressure iscarried out at a pressure of about 100 N/cm² and a heating temperatureof about 70-100° C.). In this state, positioning of the wiring pattern303 of the printed wiring board 300 and the protruding electrode 202 ofthe IC 201 is carried out.

FIG. 2(B) shows a state in which the IC 201 is temporarily press-fit tothe printed wiring board 300. The temporary press-fitting for the IC 201is carried out by only pressurization or heating with a pressure(heating temperature is about 70-100° C.).

FIG. 2(C) shows a state in which the IC 201 is finally press-fit to theprinted wiring board 300. The final press-fitting of the IC 201 iscarried out by heating with a pressure, and because the temperature atthis time is higher than the glass transition temperature of theanisotropic conductive film, the binder flows. Because at this time, noconductive particles 205 are nipped between the protruding electrodes202 of the IC 201 and the wiring pattern 303 of the printed wiring board300, all the conductive particles 205 flow. Thus, when the gap betweenthe wiring pattern 303 of the printed wiring board 300 and theprotruding electrode 202 of the IC 201 coincides with the diameter ofthe conductive particle 205, the flowing conductive particles 205 to thegap are nipped therebetween. Therefore, the conductive particles 205 donot exist in every gap between the wiring pattern and protrudingelectrode.

FIG. 2(D) shows a state in which the anisotropic conductive film ishardened. If heating with a pressure is carried out in the finalpress-fitting, resin is hardened after a flow. The series of these stepsis a connecting process.

Therefore, if electrical connection via the conductive particles isachieved regardless of a slight unevenness of the printed wiring boardwhich is an object and a slight unevenness of the protruding electrodeof the IC, it can be considered that a reliability sufficient forpractical use can be obtained even on a printed wiring board whose costis suppressed.

SUMMARY OF THE INVENTION

Accordingly, the present invention has been achieved in views of theabove problems, and therefore, it is an object of the invention toprovide an electrical connecting member and electrical connecting methodcapable of achieving electrical connection via conductive particlesregardless of a slight unevenness of an object material.

To achieve the above object, according to a first aspect of the presentinvention, there is provided an electrical connecting device forelectrically connecting an electrical connecting portion of a firstobject to an electrical connecting portion of a second object, theelectrical connecting device comprising a film-like adhesive layer to bedisposed on the first object and constituted of a plurality ofconductive particles and a binder containing the conductive particles;and paste disposed on the film-like adhesive layer and having afluidity.

According to the first aspect of the invention, the film-like adhesivelayer and paste are possessed to achieve electrical connection betweenthe electrical connecting portion of the first object and the electricalconnecting portion of the second object.

The film-like adhesive layer is an adhesive layer to be disposed on thefirst object and constituted of a plurality of conductive particles anda binder containing the conductive particles. The paste is disposed onthe film-like adhesive layer and has a fluidity.

Thus, only by disposing the film-like adhesive layer on the first objectand then paste on the film-like adhesive layer, in the electricalconnecting portions of the first and second objects, the paste having afluidity is nipped between the first object and second object and flows,so that the conductive particles in the film-like adhesive layer are notmoved but only the paste flows. Therefore, regardless of a slightunevenness in the first object, the first object and second object canbe closely fit to each other, and the electrical connecting portion ofthe first object can be electrically connected to the electricalconnecting portion of the second object positively by using theconductive particles in the film-like adhesive layer.

Preferably, according to a second aspect of the present invention, eachof the conductive particles has an almost uniform diameter. According toa third aspect of the present invention, preferably, the material of thepaste is the same adhesive agent as the material of the binder of thefilm-like adhesive layer.

As a result, when the paste and the binder in the film-like adhesivelayer are heated with a pressure, they react therewith so as to affixthe first object and second object to each other. Because the conductiveparticles have almost uniform diameter, the electrical connectingportion of the first object can be connected to the electricalconnecting portion of the second object securely such that theypositively nip the conductive particles therebetween and are notfloated.

According to a fourth aspect of the present invention, preferably, thethickness of the film-like adhesive layer is set almost equal to orlarger than the diameter of each of the conductive particles.

As a result, a case in which any conductive particle projects from thefilm-like adhesive layer is eliminated.

According to a fifth aspect of the present invention, preferably, theviscosity of the paste is set to be smaller than the viscosity of thefilm-like adhesive layer.

As a result, the paste flows with a precedence in a gap between thefirst object and second object and hence the film-like adhesive layer isnot moved, thereby making it possible to hold the conductive particlesfirmly thereat.

According to a sixth aspect of the present invention, preferably, theelectrical connecting portion of the first object is a wiring pattern ona circuit substrate, the electrical connecting portion of the secondobject is an protruding electrode of an electronic part and theconductive particles in the film-like adhesive layer electricallyconnects the wiring pattern of the circuit substrate to the protrudingelectrodes of the electronic part.

As a result, the wiring pattern of the circuit substrate and theprotruding electrodes of the electronic part can be electricallyconnected to each other by using the conductive particles in thefilm-like adhesive layer.

According to the third aspect of the present invention, a meltingtemperature of the paste is preferably set lower than the meltingtemperature of the film-like adhesive layer.

According to a seventh aspect of the present invention, there isprovided an electrical connecting method for electrically connecting anelectrical connecting portion of a first object to an electricalconnecting portion of a second object, the electrical connecting methodcomprising the steps of: adhesive layer allocation step for allocating afilm-like adhesive layer constituted of a plurality of conductiveparticles and a binder containing the conductive particles on theelectrical connecting portion of the first object; paste allocation stepfor allocating paste having fluidity on the film-like adhesive layer;and connecting step for heating with a pressure for electricallyconnecting the electrical connecting portion of the first object to theelectrical connecting portion of the second object through theconductive particles in the film-like adhesive layer.

According to the seventh aspect of the invention, at the adhesive layerallocation step, the film-like adhesive layer constituted of a pluralityof the conductive particles and a binder containing the conductiveparticles is disposed on the electrical connecting portion of the firstobject.

At the paste allocation step, the paste having the fluidity is disposedon the film-like adhesive layer.

At the connecting step, heating with a pressure is carried out toelectrically connect the electrical connecting portion of the firstobject to the electrical connecting portion of the second object by theconductive particles in the film-like adhesive layer.

As a result, only by disposing the film-like adhesive layer on the firstobject and then paste on the film-like adhesive layer, in the electricalconnecting portions of the first and second objects, the paste havingthe fluidity is nipped between the first object and second object andflows. Thus, because only the paste flows while the conductive particlesin the film-like adhesive layer are not moved, the first object andsecond object can be closely fit to each other even if there is slightunevenness in the first object, so that the electrical connectingportion of the first object can be electrically connected to theelectrical connecting portion of the second object surely by using theconductive particles in the film-like adhesive layer.

According to an eighth aspect of the present invention, preferably, theconnecting step comprises a first pressure heating step for heating at atemperature below a glass transition temperature of a binder and pastewith a pressure; and a second pressure heating step for heating at atemperature above the glass transition temperature of the binder andpaste with a pressure.

As a result, because the binder and paste are heated at a temperaturebelow the glass transition temperature at the first pressure heatingstep, they are hardened only temporarily.

Because at the second pressure heating step, the binder and paste areheated with a pressure at a temperature higher than the glass transitiontemperature of the binder and paste, the binder and paste are hardenedcompletely.

According to a ninth aspect of the present invention, preferably, thebinder and paste are of the same or almost equal component.

According to an eleventh aspect of the present invention, preferably,the connecting step comprises a first pressure heating step for heatingat a temperature below the melting temperature of the binder and abovethe melting temperature of the paste with a pressure; and thereafter asecond pressure heating step for heating at a temperature above areaction starting temperature of the binder and paste with a pressure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing an example of electrical connection in aconventional electronic device;

FIG. 2 is a diagram showing other example of electrical connection in aconventional electronic device;

FIG. 3 is a diagram showing an example of an electronic device having anelectrical connecting device according to the present invention;

FIG. 4 is a diagram showing an example of electrically connecting theelectronic device using the electrical connecting device; and

FIG. 5 is a flow chart showing an example of the electrical connectingmethod of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Hereinafter, preferred embodiments of the present invention will bedescribed in detail with reference to the accompanying drawings.

Meanwhile, although the embodiments which will be described below areprovided with various preferred technical limitations because they arepreferred embodiments of the present invention, the scope of the presentinvention is not restricted to these embodiments as long as there is noparticular description about limiting the present invention.

FIG. 3 shows an example of an electronic device 150 electricallyconnected according to a preferred embodiment of an electricalconnecting device 100 of the present invention. This electronic device150 comprises a printed wiring board 4 and an IC (integrated circuit) 2which is an example of electronic parts.

A wiring pattern 5 with a predetermined pattern is formed on a surface4A of the printed wiring board 4. This wiring pattern 5 is an electricalwiring pattern made of for example, aluminum or copper.

A plurality of protruding electrodes 3 are provided on a surface 2A ofthe IC 2. Each of the protruding electrodes 3 is called a bump and theprotruding electrodes 3 are disposed so as to protrude corresponding tothe wiring pattern 5 of the printed wiring board 4.

The printed wiring board 4 corresponds to a first object and the wiringpattern 5 of the printed wiring board 4 corresponds to the wiringpattern of the circuit substrate. On the other hand, the IC 2 is anelectronic part corresponding to a second object. The electricalconnecting device 100 has a function for electrically connecting thewiring pattern 5 of the printed wiring board 4 with the protrudingelectrodes 3 of the IC 2 and positively bonding the printed wiring board4 to the IC 2 mechanically.

Next, the electrical connecting device 100 will be described.

As shown in FIG. 3, the electrical connecting device 100 is constitutedof a film-like adhesive layer 6 and a paste 9. The film-like adhesivelayer 6 is a film-like material to be disposed on the surface 4A of theprinted wiring board 4 and the film-like adhesive layer 6 is attached tothe one surface 4A so as to cover the wiring pattern 5.

The film-like adhesive layer 6 contains conductive particles 7 and abinder 8. The binder 8 includes a number of or a plurality of theconductive particles 7. Each of the conductive particles 7 is aspherical particle produced by plating, for example, a plastic resinparticle (5 μm in diameter) with Ni (300-1000 Å thick) and furtherplating with Au (300-1000 Å thick) or a metallic powder (5-10 μm) of Ni.

The binder 8 contains a plurality of or a number of conductive particles7 in a condition that they are not moved therein. The binder 8 is madeof, for example, thermosetting type epoxy resin having electricalinsulation property.

Preferably, it is desired that a thickness D of this binder 8 is set tobe slightly larger than or equal to a diameter d of the conductiveparticles 7. Consequently, the conductive particles 7 are completelycontained in the binder 8 serving as an electrically insulating layer sothat they are not protruded therefrom.

As shown in FIG. 3, preferably the conductive particles 7 are arrangeduniformly in the binder 8.

The paste 9 is coated on the film-like adhesive layer 6. As the materialof the paste 9, preferably, bonding material of adhesive material havingthe same components as the binder 8 and an electrical insulationproperty is used. That is, the paste 9 is made of, for example,thermosetting type epoxy resin. Namely, for the binder 8 and paste 9,preferably, the same reactive adhesive agent which carries out the samereaction at the same time when they are pressurized and heated may beused.

Preferably, the viscosity of the paste 9 is set lower than that of thebinder 8. That is, the paste 9 has a higher fluidity than the binder 8.When the IC 2 is pressed to the one surface 4A of the printed wiringboard 4 via the electrical connecting device 100, only the paste 9 flowsbetween the film-like adhesive layer 6 and the one surface 2A of the IC2 so that the gap is filled therewith.

Next, a preferred embodiment of an electrical connecting method forelectrically connecting the IC 2 to the printed wiring board 4 with theelectrical connecting device 100 will be described with reference toFIGS. 4 and 5.

Adhesive Layer Allocation Step S1 of FIG. 5

At step S1, the film-like adhesive layer 6 is attached to the onesurface 4A of the printed wiring board 4 as shown in FIGS. 3 and 4(A).In this case, the film-like adhesive layer 6 is attached so as to coverthe wiring pattern 5. In this state, the conductive particles 7 arecontained completely in the binder 8.

Paste Allocation Step S2

At this step S2, as shown in FIGS. 4(A) and 3, the paste 9 is disposedand coated on the film-like adhesive layer 6. When the paste 9 iscoated, it is located in the center portion of the film-like adhesivelayer 6 such that it is swollen up.

Positioning Step S3

At step S3, as shown in FIGS. 4(A) and 3, the IC 2 is positioned on theprinted wiring board 4. That is, the protruding electrodes 3 of the IC 2are positioned at positions corresponding to the wiring pattern 5.

Connecting Step S4

The connecting step S4 comprises first pressure heating step S5 andsecond pressure heating step S6.

At the first pressure heating step S5, as shown in FIG. 4(B), the IC 2is placed on the film-like adhesive layer 6, so that the paste 9 isspread over along the film-like adhesive layer 6. Thus, as shown in FIG.4(B), the gap between the one surface 2A of the IC 2 and the film-likeadhesive layer 6 is almost filled with the paste 9. The reason of thisis that because the viscosity of the paste 9 is lower than that of thefilm-like adhesive layer 6, only the paste 9 is spread around so thatthe gap between the one surface 2A of the IC 2 and the film-likeadhesive layer 6 is filled with the paste 9. In a state shown in FIG.4(B), the binder 8 and paste 9 are temporarily hardened just. Therefore,a heat to be applied at this time is of a temperature lower than a glasstransition temperature of the paste 9 and binder 8, for example, 80° C.for about three seconds. At that time, a pressure of about 3 kg/mm² isapplied to an area of the protruding electrodes 3 of the IC 2 to beconnected to the wiring pattern 5 of the printed wiring board 4 via theconductive particles 7 while they are being heated.

Next, at the second pressure heating step S6, as shown in FIG. 4(C), astronger pressure is applied and the binder 8 and paste 9 are heated ata higher temperature. A temperature at this time is higher than theglass transition temperature of the binder 8 and paste 9, and they areheated, for example, 180-230° C. for 20-30 seconds. At that time, apressure of about 3 kg/mm2 is applied to an area of the protrudingelectrodes 3 to be connected to the wiring pattern 5 of the printedwiring board 4 via the conductive particles 7. As a result, because,preferably, the binder 8 and paste 9 have the same or similarcomponents, they can be hardened at substantially the same time.Consequently, as shown in FIG. 4(D), each of the protruding electrodes 3can be electrically connected to the wiring pattern 5 by using theconductive particles 7 in the film-like adhesive layer 6.

When the IC 2 is heated while being pressurized to the printed wiringboard 4 side, only the paste 9 coated on the film-like adhesive layer 6is made fluid. Therefore, even if there is slight unevenness on the IC 2and printed wiring board 4, electrical insulation between the IC 2 andthe printed wiring board 4 can be sufficiently secured. Because only thepaste 9 coated on the film-like adhesive layer 6 is made fluid, even ifthere is slight unevenness on the IC 2 and the printed wiring board 4,void (air region) between the IC 2 and printed wiring board 4 is reducedthereby reliability being improved.

Further, because the paste 9 and binder 8 are hardened by the pressureheating, the paste 9 and binder 8 having an adhesiveness bond and fixthe IC 2 firmly to the printed wiring board 4 side.

At the first pressure heating step S5 of FIG. 4(B), the conductiveparticles 7 are located such that they are nipped between the protrudingelectrodes 3 and wiring pattern 5. Then, if a strong pressure is furtherapplied in FIG. 4(C), only the conductive particles 7 located betweenthe protruding electrodes 3 and wiring pattern 5 are nipped firmlybetween the protruding electrodes 3 and the wiring pattern 5 so that theprotruding electrodes 3 are electrically connected to the wiring pattern5, and the other conductive particles 7 are moved slightly to theperiphery thereof. Even if there is slight unevenness on the IC 2 andprinted wiring board 4, that unevenness of each electrode is absorbedbecause the conductive particles 7 exist between the IC 2 and electrodesof the printed wiring board 4, thereby securing a connecting reliabilitysufficiently.

If the thickness of the adhesive layer 6 is made equal to the diameterof the conductive particle 7 according to the preferred embodiment ofthe present invention, the conductive particles 7 are nipped furthersecurely between the protruding electrodes 3 of the IC 2 and the wiringpattern 5 formed on the printed wiring board 4.

If according to the preferred embodiment of the present invention, theviscosity of the binder 8 of the adhesive layer 6 is set higher whilethe viscosity of the paste 9 is lower, the paste 9 is more likely toflow upon temporary pressure-fitting, so that the conductive particles 7are nipped further securely between the protruding electrodes 3 of theIC 2 and the wiring pattern 5 formed on the printed wiring board 4.

If according to the preferred embodiment of the present invention, thecomponent of the binder 8 of the adhesive layer 6 is made the same as oralmost same to the component of the paste 9, even if the binder 8 andpaste 9 are mixed when they are heated and made fluid, the connectingreliability is not affected badly.

If according to the preferred embodiment of the present invention, atemperature at the time of the first pressurization is lower than theglass transition temperature of the binder 8, the adhesive layer 6 iscapable of maintaining the film shape so that the conductive particles 7are nipped between the protruding electrodes 3 of the IC 2 and thewiring pattern 5 formed on the printed wiring board 4.

As described above, according to the present invention, even if there isslight unevenness in the wiring pattern 5 formed on the printed wiringboard 4, it is possible to realize a connecting member which can achievean electrical connection via the conductive particles 7 and a connectingmethod thereof.

By using the adhesive layer 6 which is a film-like connecting resinhaving a high viscosity, the conductive particles 7 having the samediameter as the film thickness of that layer and the paste 9 which isthe connecting resin having a low viscosity, the conductive particles 7can be interposed securely between the protruding electrode of anelectronic part like a bare chip and the conductive pattern of anobject, thereby obtaining an electrical conductivity therebetween.

The adhesive layer containing the conductive particles, the thickness ofwhich is substantially same as the diameter of the conductive particle,attached to a predetermined position of the object wiring pattern andthe paste constituted of the same reactive adhesive as the component ofthe binder of the above adhesive layer coated on the adhesive layer arepositioned such that the object wiring pattern opposes the protrudingelectrode of the IC, and after a pressure is applied, the electricalconnection is carried out by heating with a pressure.

In the first pressurization, after the connecting members are heated ata temperature lower than the glass transition temperature thereof undera pressure, it is permissible to harden the connecting member by heatingunder a pressure.

Consequently, upon the first pressurization, only the paste constitutedof the same reactive adhesive agent as the component of the binder inthe adhesive layer flows, so that the protruding electrodes of the ICand the object wiring pattern are electrically connected to each otherthrough the conductive particles in the adhesive layer containing theconductive particles, having the same thickness as the diameter of theeach of the not moved conductive particles.

According to the embodiment of the present invention, the viscosity ofthe binder in the adhesive layer is made higher while the viscosity ofthe paste is made lower.

As a result, only the paste constituted of the same reactive adhesiveagent as the component of the binder of the adhesive layer having a lowviscosity flows when a pressure is applied at first. As a result, theprotruding electrodes of the IC and the object wiring pattern can beelectrically connected to each other through the conductive particles inthe adhesive layer having a higher viscosity and less likely to flow andhaving the same thickness as the diameter of the conductive particles.

Further, according to the embodiment of the present invention, theconductive adhesive layer having the electrical conductivity is made tohave almost the same thickness as the diameter of the conductiveparticles existing in the adhesive layer.

As a result, because only the conductive particles contributing toelectrical connection exist on the bottommost face when fine pitch iscarried out, the number of the conductive particles existing in thatadhesive layer can be increased. Further, because the total number ofthe conductive particles can be reduced as compared to a conventionaladhesive member, an insulation property relative to adjacent electrodescan be obtained more easily.

According to the embodiment of the present invention, the meltingtemperature of the binder of the adhesive layer is made higher and themelting temperature of the paste is made lower.

That is, according to the embodiment of the present invention,preferably, the connecting step includes the first pressure heating stepfor heating at a temperature below the melting temperature of the binderand above the melting temperature of the paste with a pressure, andthereafter the second pressure heating step for heating at a temperaturehigher than the reaction starting temperature of the binder and pastewith a pressure.

As a result, if heating is carried out at a temperature below themelting temperature of the binder and above the melting temperature ofthe paste with a pressure at the time of the first pressure heating,only the paste flows more, so that the protruding electrodes of the ICand the object wiring pattern can be electrically connected through theconductive particles in the adhesive layer containing the conductiveparticles, having the same thickness as the diameter of the conductiveparticles which do not flow below the melting temperature.

The present invention is not limited to the above embodiments.

Although, according to the above embodiment, the first object is theprinted wiring board 4 having the wiring pattern 5 and the second objectis the IC 2 having the protruding electrodes 3, it is permissible to usea different matter for each object. For example, as the first object, itis permissible to use other kind like a glass substrate having a wiringpattern instead of the printed wiring board. Further, as the secondobject, it is permissible to use other electronic part in place of theIC2.

Further, as a type of the protruding electrode 3, for example, a platingbump may be employed. The shape of the conductive particles 7 is notrestricted to the spherical shape, but other type may be employed.

As described above, according to the present invention, the electricalconnection via the conductive particles can be achieved securelyregardless of a slight unevenness of an object.

Having described preferred embodiments of the invention with referenceto the accompanying drawings, it is to be understood that the inventionis not limited to those precise embodiments and that various changes andmodifications could be effected therein by one skilled in the artwithout departing from the spirit or scope of the invention as definedin the appended claims.

What is claimed is:
 1. An electrical connecting method for electricallyconnecting an electrical connecting portion of a first object to anelectrical connecting portion of a second object, the electricalconnecting method comprising the steps of: presenting a film-likeadhesive layer comprising a binder containing a plurality of conductiveparticles; allocating the film-like adhesive layer on the electricalconnecting portion of the first object; allocating a paste havingfluidity on the film-like adhesive layer to form a resultingcombination; and heating the resulting combination with a pressure toelectrically connect the electrical connecting portion of the firstobject to the electrical connecting portion of the second object throughthe conductive particles in the film-like adhesive layer.
 2. Theelectrical connecting method of claim 1, wherein heating the resultingcombination comprises, heating at a temperature below a glass transitiontemperature of the binder and the paste with a pressure, and heating ata temperature above the glass transition temperature of the binder andthe paste with a pressure.
 3. The electrical connecting method of claim1, wherein the binder and the paste are of the same or almost samecomponent.
 4. The electrical connecting method of claim 1, wherein amelting temperature of the paste is set to be lower than a meltingtemperature of the film-like adhesive layer.
 5. The electricalconnecting method of claim 4, wherein heating the resulting combinationcomprises, heating at a temperature below a melting temperature of thebinder and above the melting temperature of the paste with a pressure,and heating at a temperature above a reaction starting temperature ofthe binder and the paste with a pressure thereafter.